Effect of exercise-induced ischemia on QT interval dispersion

Roukema, Gert; Singh, Jagmeet P.; Meijs, M. M.; Carvalho, Celso Morato de; Hart, George

doi:10.1016/s0002-8703(98)70347-3

Cited by 76 publications

(32 citation statements)

References 23 publications

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“…The conclusion of reduced O 2 availability is supported by the small heart rate rise during hypocapnia that was abolished by giving O 2 in hypocapnia. This reduced oxygen availability may be sufficient to alter myocardial contractility and ventricular repolarization (46) and, hence, reduce T wave amplitude. The fact that giving O 2 during hypocapnia failed to reverse the T wave reduction is itself inconclusive, because breathing O 2 only at atmospheric pressure could not completely counteract the reduced O 2 availability in hypocapnia.…”

Section: Ajp-regul Integr Comp Physiolmentioning

confidence: 99%

Hypocapnia reduces the T wave of the electrocardiogram in normal human subjects

Rutherford¹,

Clutton-Brock²,

Parkes³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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During voluntary hyperventilation in unanesthetized humans, hypocapnia causes coronary vasoconstriction and decreased oxygen (O 2) supply and availability to the heart. This can induce local epicardial coronary artery spasm in susceptible patients. Its diagnostic potential for detection of early heart disease is unclear. This is because such hypocapnia produces an inconsistent and irreproducible effect on electrocardiogram (ECG) in healthy subjects. To resolve this inconsistency, we have applied two new experimental techniques in normal, healthy subjects to measure the effects of hypocapnia on their ECG: mechanical hyperventilation and averaging of multiple ECG cycles. In 15 normal subjects, we show that hypocapnia (20 Ϯ 1 mmHg) significantly reduced mean T wave amplitude by 0.1 Ϯ 0.0 mV. Hypocapnia also increased mean heart rate by 4 beats/min without significantly altering blood pressure, ionized calcium or potassium levels, or the R wave or other features of the ECG. We therefore provide the first unequivocal demonstration that hypocapnia does consistently reduce T wave amplitude in normal, healthy subjects. coronary circulation; carbon dioxide; angina DURING VOLUNTARY HYPERVENTILATION in unanesthetized humans, hypocapnia causes coronary vasoconstriction and decreased oxygen (O 2 ) supply and availability to the heart. Thus cardiac catheterization studies show that voluntary hyperventilation [to partial pressure levels of carbon dioxide in arterial blood (Pa CO 2 ) of 20 mmHg] increases coronary vascular resistance by 17% (47), decreases coronary blood flow by 30% (47), and increases the affinity of hemoglobin for O 2 by 25% (35). During voluntary hyperventilation, hypocapnia can induce local epicardial coronary artery spasm in single or multiple vessels with associated ST displacement, both in susceptible patients with voluntary hyperventilation syndrome (but without symptoms of heart disease) (15, 24) and in the rare group of patients with Prinzmetal's variant angina (29,59).It is unclear whether this effect has any diagnostic potential for early coronary heart disease. This is because numerous studies in healthy subjects report that hypocapnia produces only inconsistent decreases in the amplitude of the ECG T wave that are not reproducible in every subject (5,6,8,16,20,22,30,49,54,58).Such inconsistency is not surprising because of the methodological difficulties inherent with voluntary hyperventilation in the variability of inflation volumes achieved and of the duration, level, and stability of hypocapnia. Variability in movement of the body surface (and its attached electrodes) relative to the heart with each inflation introduces a crucial artifact that alone might explain this inconsistency. These difficulties are compounded by the lack of a standardized procedure for ECG analysis during hyperventilation. It is unclear precisely how many ECG complexes were measured, how they were selected, and what was their precise relationship to the inflation cycle (6,16,58,60).We have therefore applied two novel ap...

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Section: Ajp-regul Integr Comp Physiolmentioning

confidence: 99%

Hypocapnia reduces the T wave of the electrocardiogram in normal human subjects

Rutherford¹,

Clutton-Brock²,

Parkes³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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“…12 There is considerable evidence that QT dispersion may indirectly reflect underlying nonhomogenecity of ventricular repolarization. 13 An increase in QT dispersion is reported to predict the occurrence of life-threatening ventricular tachyarrhythmias and sudden cardiac death in patients with ischemic heart disease. 14 Tikiz, et al had studied the patients with single vessel CAD had wider resting QT dispersion when compared to control group, which further increased significantly with exercise.…”

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confidence: 99%

Prolonged QTc Dispersion Correlates with Coronary Artery Disease in Acute ST Elevated Myocardial Infarction (STEMI)

et al. 2013

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Background: It has been found that there is strong association of QT dispersion and QT dispersion ratio with extent and severity of coronary artery disease. Qualitative importance of QTc dispersion on the base line ECG in patients with MI is recognized clinically but quantification of this phenomenon is less commonly used in clinical practice, which might be a better independent risk predictor of this group of patients. Methods: A total of 100 patients were selected, Study populations sub-divided into two groups on the basis of QTc dispersion. In group I (comparison group): QTc dispersion is <60 milliseconds (msec) in group II (study group) : QTc dispersion e60milliseconds(msec). 50 patients in each group. QT dispersion was calculated on standard resting 12 lead ECGs. QT interval was measured from the beginning of the inscription of the QRS complex to the point at which the T wave returned to the isoelectric line. Angiographic severity of coronary artery disease was assessed by- Vessel score, Friesinger score and Leaman score. Interpretation of coronary angiogram was reviewed by at least two cardiologists. . Results: The mean vessel score for group I patients was 1.16±0.68 and that of group II patients was 2.30±0.64 and the mean difference was statistically significant (p<0.05). Patients those had single vessel involvement had mean QTc dispersion 57.05, patients those had double vessel disease mean QTc dispersion was 102.00 and patients those had triple vessel involvement had mean QTc dispersion 177.60. There was a strong positive correlation with the QTc dispersion and increasing number of vessel involvement (Pearsons correlation coefficient). The mean Friesinger score for group I patients was 4.84±2.56 and that of group II patients was 9.80±2.60. The mean difference was significantly (p<0.05) higher in group II patients. There was a strong positive correlation between the QTc dispersion and Leaman score (Pearsons correlation coefficient). In group I patients 56% had insignificant coronary artery disease and 44% had significant coronary artery disease defined by Friesinger index (n=100). In group II patients 6% had Insignificant coronary artery disease & had 94% significant coronary artery disease. Conclusion: QTc dispersion>60 ms had independent predictive value for the severity of coronary artery disease. The greater the QTc dispersion the higher the number of coronary artery involvement. We observed that there is a positive correlation between prolonged QT dispersion and coronary artery disease severity in terms of Vessel score, Friesinger score, Leaman score. DOI: http://dx.doi.org/10.3329/cardio.v5i2.14322 Cardiovasc. j. 2013; 5(2): 173-181

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“…Ischemic myocardium may play a significant role as an arrhythmic substrate due to intracardiac inhomogeneities of repolarization (Roukema et al 1998). Asymptomatic myocardial ischemia is of a high prevalence among diabetic patients even in the lack of significant coronary artery stenosis (Koistinen 1990).…”

Section: Discussionmentioning

confidence: 99%

“…After a prolonged period of diabetes it is commonly accompanied with multiple cardiovascular complications such as coronary artery disease, diabetic cardiomyopathy, and cardiac autonomic neuropathy (Ali Raza and Movahed 2003). Myocardial ischemia can lead to electrophysiological heterogeneity and asynchronism in ventricular myocardium (Roukema et al 1998). In addition, altered sympathovagal balance in the presence of cardiac autonomic neuropathy may contribute to electrophysiological heterogeneity of the myocardium (Ewing et al 1991).…”

mentioning

confidence: 99%

Hyperbaric Oxygen Therapy Decreases QT Dispersion in Diabetic Patients

Kardeşoğlu

Aparcı

Uzun

et al. 2008

Tohoku J. Exp. Med.

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Diabetes mellitus is frequently associated with the malignant ventricular arrhythmias and sudden death. The QT dispersion is the difference between the longest and shortest QT interval calculated from the standard 12-lead electrocardiogram. The QT dispersion is suggested as an index of myocardial electrical activity. An increase in QT dispersion is associated with the malignant ventricular arrhythmias and sudden cardiac death. Diabetic patients receive hyperbaric oxygen (HBO) therapy for non-healing lower extremity ulcers. The aim of this study was to determine the effect of HBO therapy on QT dispersion in diabetic patients. Thirty diabetic patients (18 male and 12 female, 59.9 ± 10 years), who were planning to undergo ten sessions of HBO therapy in two weeks for non-healing lower extremity ulcers, were consecutively enrolled into the study. The 12-lead resting electrocardiography recordings were taken before the first HBO therapy and after the 10th HBOtherapy session. QT intervals were measured on electrocardiogram. QT intervals were corrected for heart rate by using Bazett's formula (corrected QT [QTc] = QT/√R -R [seconds]). QTc dispersion was significantly decreased from 59.8 ± 17.4 msec to 52.2 ± 15.5 msec after ten sessions of HBO therapy ( p < 0.05). However, maximum QTc, minimum QTc and mean QTc did not change significantly after HBO therapy. We have concluded that HBO therapy may reduce the risk of malignant ventricular arrhythmia and sudden cardiac death in diabetic patients when applied repetitively. hyperbaric oxygenation; diabetes mellitus; QT interval; electrocardiography.Tohoku

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Effect of exercise-induced ischemia on QT interval dispersion

Cited by 76 publications

References 23 publications

Hypocapnia reduces the T wave of the electrocardiogram in normal human subjects

Hypocapnia reduces the T wave of the electrocardiogram in normal human subjects

Prolonged QTc Dispersion Correlates with Coronary Artery Disease in Acute ST Elevated Myocardial Infarction (STEMI)

Hyperbaric Oxygen Therapy Decreases QT Dispersion in Diabetic Patients

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